Numerous applications exist in which it is desired to form repeating patterns having a small pitch (for example, a pitch of less than about 50 nanometers). For instance, integrated circuit fabrication may involve formation of a repeating pattern of memory-storage units (i.e., NAND unit cells, dynamic random access [DRAM] unit cells, cross-point memory unit cells, etc.).
Photolithography is a conventional method utilized for fabrication of integrated components. Photolithography utilizes light to pattern a photosensitive material. The photolithographically-patterned photosensitive material may then be utilized as a mask for patterning underlying materials to form the integrated circuit components.
A continuing goal of integrated circuit fabrication is to increase integrated circuit density, and accordingly to decrease the size of individual integrated circuit components. There is thus a continuing goal to form patterned masks having increasing densities of individual features. In cases in which the patterned masks comprise repeating patterns of features, there is a continuing goal to form the repeating patterns to higher density, or in other words, to decrease the pitch.
If only photolithography is utilized to pattern integrated circuit components, integrated circuit density cannot increase beyond a threshold dictated by the minimum attainable feature size obtainable utilizing the particular photolithographic technology. The minimum feature size is dictated by, for example, a wavelength utilized during the photolithography.
Several methods have been developed which can be utilized in combination with photolithography to push the minimum attainable feature size to smaller dimensions than may be achieved with photolithography alone. Among such methods is a procedure comprising utilization of a block copolymer to form a pattern between a pair of photolithographically-patterned features. The pattern created with the block copolymer may be at higher density than is achievable with photolithography, and thus block copolymer may be utilized to create higher integrated circuit densities than are achievable with photolithography alone.
It would be desirable to develop new methods of forming patterns with block copolymers which enable repeating patterns to be formed to high density. It would be further desirable for such methods to be readily applicable for semiconductor device fabrication.